Alloy steels



nited States Patent Ofifice 2,693,413 Patented Nov. 2, 1954 ALLOY STEELS Henry William Kirlrby and Charles Sykes, Shetlield, England, assignors to Firth-Vickers Stainless Steels Limited, Shefilield, England, a British company No Drawing. Application March 30, 1951, Serial No. 218,529

Claims priority, application Great Britain January 31, 1951 3 Claims. (Cl. 75-128) This invention is concerned with improvements relating to alloy steels.

The specification of our copending United States patent application Serial No. 126,698, filed November 10, 1949, now Patent No. 2,590,835, describes the invention comprising a forgeable ferritic alloy steel possessing high creep resistance at temperatures at least up to 700 C., and having a composition including as essential constituents carbon 0.05 to 0.5%, chromium 4 to 20%, molybdenum up to 3% interchangeable with tungsten up to 3%, niobium up to 2.5%, boron up to 0.5% and vanadium up to 2%.

In the aforesaid specification No. 126,698 it was indicated that the alloy composition might also include silicon up to 3%, manganese up to 4%, and cobalt up to 10%, and the preferred proportions of the various constituents was said to be as follows:

Per cent to .25 to 1.5 to 1.5 to 1.5 to 14.0 to 1.5 to 0.3 to 3.0

Carbon .10 Silicon Manganese Nickel Chromium PP PPP QH Ig I IUI Vanadium Tungsten Niobium Nitrogen Boron 0.025 to 0.10 Cobalt nil to 5 Iron Remainder The present invention comprises improvements in or modifications of the foregoing invention forming the subject matter of our prior application.

According to the principal feature of the present invention the carbon content of alloys within the broad range of composition referred to above, is maintained within the limits of 0.07-0.12%. By this modification a softer final product is obtained.

Further modifications in the limits of proportions of certain of the constituents of the alloy-still within the broad range previously indicatedhave also been found It will be noted that in the above preferred composition no boron is present.

Like the alloys of application Serial No. 126,698 aforesaid, the alloys of the present invention are of the ferritic type, that is to say they are magnetic, can be hardened and tempered and have thermal expansion properties similar to those of carbon and low alloy steels. Alloys within the invention possess high creep resistance at temperatures at least up to 700 C. In addition to high creep resistance, the alloys of this invention possess high tensile and proof properties and good scale resistance. They are suitable for many higher temperature applications, particularly in jet engines. In general, the high temperature properties of the present alloys are only a little inferior to those of alloys having the composition preferred in our prior application. Stress rupture tests on alloys within the present preferred range, after suitable heat treatment, gave the following results:

Test Tem- Rupture Stress perature, Strength,

0. hrs.

15 tons/sq. in 650 -200 The following is an example of a specific alloy within the invention:

The above alloy, after air or oil hardening from 1160 C. followed by a tempering treatment at 675 C. was found to possess the desirable creep resistance properties previously indicated herein.

We claim:

1. A forgeable ferritie alloy steel possessing high creep resistance at temperatures at least up to 700 C. composed essentially of carbon 0.07-0.12%, chromium 4- 20%, molybdenum interchangeable with tungsten 0.5- 3%, niobium 0.2-2.5 vanadium 0.l2%, nitrogen 0.05-0.l0%, and the remainder iron, with incidental impurities in ordinary amounts, which do not affect the physical properties and high temperature characteristics of the steel.

2. A forgeable ferritic alloy steel possessing high creep resistance at temperatures at least up to 700 C. and having a composition comprising carbon 0.07-0.12%, silicon 0.50-1.0%, manganese 0.50-1.0%, nickel 0.5- 1.5%, chromium 9l1%, molybdenum 0.4-1.0%, vanadium 0.1-0.3%, niobium including any residual tantalum 0.2-0.6%, nitrogen ODS-0.10%, and the remainder substantially all iron.

3. A forgeable ferritic alloy steel comprising carbon about 0.10%, silicon about 0.5%, manganese about 1.0%, nickel about 0.7%, chromium about 10.5%, molybdenum about 0.75%, vanadium about 0.15%, niobium about 0.5%, nitrogen about 0.08%, and the remainder iron, with incidental impurities in ordinary amounts, which do not affect the physical properties and high temperature characteristics of the steel.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,120,554 Franks Dec. 20, 1938 2,140,905 Franks Dec. 20, 1938 2,212,496 De Vries Aug. 27, 1940 2,432,614 Franks Dec. 16, 1947 2,513,935 Harris July 4, 1950 

1. A FORGEABLE FERRITIC ALLOY STEEL POSSESSING HIGH CREEP RESISTANCE AT TEMPERATURES AT LEAST UP TO 700* C. COMPOSED ESSENTIALLY OF CARBON 0.07-0.12%, CHROMIUM 420%, MOLYBDENUM INTERCHANGEABLE WITH TUNGSTEN 0.53%, NIOBIUM 0.2-2.5%, VANADIUM 0.1-2%, NITROGEN 0.05-0.10%, AND THE REMAINDER IRON, WITH INCIDENTAL IMPURITIES IN ORDINARY AMOUNTS, WHICH DO NOT EFFECT THE PHYSICAL PROPERTIES AND HIGH TEMPERATURE CHARACTERISTICS OF THE STEEL. 